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Biomedical subjects

W R Martin

Publications and source records attributed to W R Martin.

At least 91 records · Page 5Linked to original sources
PubMed1990

Cortical glucose metabolism in Parkinson's and Alzheimer's disease.

Characteristic regional patterns of decreased cerebral glucose metabolism (rCMRG) have been described in a variety of neurodegenerative conditions associated with dementia. The present study was undertaken to determine whether the metabolic pattern in Parkinson's disease is altered by the presence of impaired cognitive function. Glucose metabolism was measured with positron emission tomography in 6 patients with Parkinson's disease and dementia (PDD), 8 patients with Parkinson's disease and normal cognition (PD), and 6 patients with Alzheimer's disease (AD). All AD patients subsequently had the diagnosis proven neuropathologically at autopsy. Correlation coefficients of the metabolic rates across 32 regions of interest were calculated between each pair of patients. Q-component analysis of the correlation matrix showed that the AD and PD groups formed two distinct clusters and that the PDD group had a metabolic pattern which was similar to that of the AD group. Comparison of standardized rCMRG values showed that the PDD group differed from the PD group in having significantly lower relative rCMRG in the left perirolandic and bilateral angular gyrus regions. There were no significant differences between the PDD and AD groups. These results suggest a similar pattern of cortical dysfunction in both Alzheimer's disease and in Parkinson's disease/dementia.

Aged↗
PubMed1990

The effects of flumazenil-precipitated abstinence on the pharmacokinetics of chronic oxazepam in dogs.

The pharmacokinetics of oxazepam was studied in naive dogs and in oxazepam-dependent dogs without and with administered flumazenil (6 mg/kg). Oxazepam is eliminated with a relatively short elimination half life (ca. 150 min) in both acutely and chronically treated dogs. It exhibits only a modest first pass metabolism (ca. 10%) and its bioavailability following oral administration is about 22%. The steady state concentration of oxazepam in chronically treated dogs was lower than was predicted from single dose studies. Flumazenil did not change the rate of absorption or elimination of oxazepam-dependent dogs. The total steady state plasma concentration of oxazepam was significantly reduced by flumazenil administration suggesting a displacement interaction between flumazenil and oxazepam.

Administration, Oral↗
PubMed1990

Dependence-producing properties of alprazolam in the dog.

Alprazolam (48 mg/kg/day) administered orally to dogs 4 times a day in equally divided doses produced physical dependence. This dependence was revealed by a precipitated abstinence syndrome which occurred after either oral administration of flumazenil (6, 18 and 36 mg/kg) or intravenous administration of a liposomal suspension of flumazenil. Flumazenil alone (18, 36 and 72 mg/kg) produced no significant signs of precipitated abstinence in naive dogs. This precipitated abstinence syndrome in alprazolam-dependent dogs was characterized by both clonic and tonic-clonic seizures. Other signs of precipitated abstinence which comprise the NPAS score were less intense in the alprazolam-dependent than in diazepam-dependent dogs. Alprazolam is extensively metabolized in the dog and does not accumulate whereas its predominant metabolite, alpha hydroxyalprazolam, does accumulate. The data suggest that alpha hydroxyalprazolam plays a role in the dependence-producing properties of alprazolam in the dog as revealed by the precipitated abstinence syndrome.

Administration, Oral↗
PubMed1990

Treatment of refractory Parkinson's disease with adrenal medullary autografts utilizing two-stage surgery.

Treatment of refractory PD with autologous adrenal medullary implants utilizing two-stage surgery warrants further investigation. This transplantation technique is associated with prolonged transplant area BBB disruption which may require a change in medical treatment strategies including the withdrawal of peripheral dopa decarboxylase inhibitors and possible intravenous or intraventricular dopamine therapy. Of 5 patients receiving adrenal medullary transplants, 3 have demonstrated varying degrees of clinical improvement which has persisted for the duration of the study. The positive correlation between clinical outcome and caudate function (i.e., 6-fluorodopa PET scans) suggests a positive influence of the transplantation procedure on the diseased striatum. Whether or not the grafted tissue remains viable for an extended period is currently being investigated utilizing 6-FDG-PET studies. Because of the presence of persistent BBB disruption, we surmise that at least viability of implanted fenestrated adrenal medullary capillaries exists. We conclude that this prolonged leakage is the result of the implanted tissue rather than the cavitation procedure as prolonged BBB disruption was not witnessed in a control group of patients with post-traumatic cerebral contusions or in Parkinson's patients subjected to thalamotomies. Whether two-stage surgery results in increased graft viability, and host neuronal sprouting, leading to prolonged clinical improvement and slowing the progression of PD awaits continued longitudinal (greater than 24 months) studies.

Adrenal Medulla↗
PubMed1990

Parkinsonism with neuroacanthocytosis.

Two patients with neuroacanthocytosis are described. One presented with parkinsonism and the other resembled diurnal dystonia of the Segawa type. Both patients responded well to dopaminomimetic therapy. A PET scan with fluorodopa revealed a nigrostriatal deficit in the first patient.

Acanthocytes↗
PubMed1990

Expression of mucin synthesis and secretion in human tracheobronchial epithelial cells grown in culture.

The effects of culture conditions on growth and differentiation of human tracheobronchial epithelial (HTBE) cells have been defined. Epithelial cells were dissociated from tissues by protease treatment and were plated on tissue culture dishes in F12 medium supplemented with insulin, transferrin, epidermal growth factor, hydrocortisone, cholera toxin, bovine hypothalamus extract, and retinol. HTBE cells did not express any mucociliary function (ciliogenesis or mucin secretion) on tissue culture plastic, but they could be passaged 3 to 5 times with a total of 10 to 25 population doublings. Cells from early passages re-express both these functions when transplanted to tracheal grafts. When tissue culture plates were coated with collagen film or collagen gel substrata, cell attachment and proliferation were stimulated. However, the expression of mucous cell function in culture occurred only when cells were plated on collagen gel substrata and vitamin A (retinol) was present in the medium. Mucous cell differentiation under optimal conditions was defined by ultrastructural studies, by immunologic studies with mucin-specific monoclonal antibodies, and by carbohydrate and amino acid compositional analyses of mucin-like glycoproteins purified from culture medium. These results demonstrate for the first time that HTBE cells can express mucin synthesis and secretion under appropriate culture conditions.

Amino Acids↗
PubMed1990

Regional cerebral glucose metabolism in major depressive disorder.

Six subjects with DSM-III defined unipolar major depressive disorder had positron emission tomography scans using 18F-2-fluoro-2-deoxy-D-glucose (2FDG) before and after treatment with imipramine. Their 12 scans were compared to the scans of six controls matched for age. Significant reductions in metabolism for subjects in the depressed group were found on scans for both the anterior and right frontal regions. significant reductions in metabolism occurred more often in the right hemisphere than the left. No significant changes in metabolism could be attributed to imipramine. In addition, absolute metabolic rates were not related to the degree of depression pre- and post-treatment. The findings suggest that hypometabolism in the frontal cortex and right hemisphere may occur in major depressive disorders.

Adult↗
PubMed1990

Cognitive change following MPTP exposure.

In a previous study, we demonstrated that patients with MPTP-induced parkinsonism (MPTP-IP) had a pattern of cognitive change similar to that in nondemented patients with idiopathic Parkinson's disease (PD). The present study addressed cognitive change in MPTP-exposed but relatively asymptomatic (MPTP-AS) individuals. We examined them for general intellectual function, construction, language, memory, executive function, attention, and reaction time, and compared their performance with data obtained in the previous study from patients with MPTP-IP and drug addict controls. Each MPTP-AS individual had some subtle parkinsonian signs, but in no case would these be sufficient for a diagnosis of PD. PET studies showed that these individuals had significantly reduced uptake of labeled 6-fluorodopa into the striatum. MPTP-AS and MPTP-IP groups performed comparably and were significantly worse than controls on tests of construction and category naming. The MPTP-AS group performed at a level between the other 2 groups on a test of executive function. The 3 groups performed comparably on all other measures. The similarity of the pattern of intellectual change in MPTP-AS to that seen in MPTP-IP and idiopathic PD supports the idea that the dopamine system mediates a specific set of cognitive functions and suggests that cognitive change can occur in the presence of few or no motor signs of parkinsonism.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1990

Tracheal catheters in patients with acquired immunodeficiency syndrome for the diagnosis of Pneumocystis carinii pneumonia.

The diagnosis of Pneumocystis carinii pneumonia (PCP) often requires bronchoscopy. In 82 consecutive human immunodeficiency virus (HIV)-positive patients suspected of having PCP, we passed a 14-F catheter into the trachea under local anesthesia without intubation, instilled saline solution, and then collected the secretions by aspiration. Bronchoscopy with collection of bronchial washings and performance of bronchoalveolar lavage (BAL) was then performed and the results were compared. The catheter results were identical with the results of BAL in 77 of 82 patients. This inexpensive technique may provide a reasonable early step in the diagnosis of PCP.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Precipitated abstinence in orally dosed benzodiazepine-dependent dogs.

The ability of graded doses of flumazenil (2, 6, 18, 36 and 72 mg/kg) and a lactose placebo to precipitate abstinence was studied in dogs treated chronically with diazepam, nordiazepam, flunitrazepam, alprazolam, oxazepam, halazepam and lorazepam by oral dosing. A scale comprised of 10 precipitated abstinence signs, the Benzodiazepine Precipitated Abstinence Scale, was developed, which yielded linear flumazenil log-dose response lines with significant slopes in dogs dependent on diazepam, nordiazepam and flunitrazepam. The effects of 18, 36 and 72 mg/kg of flumazenil in otherwise drug naive dogs were studied. In naive dogs, the most prominent effect of flumazenil was to reduce activity. All benzodiazepines studied produced dependence that was characterized by signs of precipitated abstinence; however, the intensity and quality of abstinence varied from one benzodiazepine to another. Precipitated abstinence in dogs treated chronically with diazepam and flunitrazepam was characterized by a dose-related increase in clonic convulsions and Benzodiazepine Precipitated Abstinence Scale scores. This pattern differed from that seen in nordiazepam- and alprazolam-dependent dogs, which showed a comparable flumazenil dose-related increase in clonic convulsion but only a modest increase in Benzodiazepine Precipitated Abstinence Scale scores. Oxazepam and lorazepam produced dependence that was less intense than that seen with the other benzodiazepines. Plasma levels of the benzodiazepines and their metabolites were repeatedly determined after single doses and during addiction cycles. Nordiazepam accumulated in diazepam- and nordiazepam-dependent dogs and alpha-OH alprazolam accumulated in alprazolam-dependent dogs. Other drugs and metabolites did not. These observations suggest that: 1) different benzodiazepines or their metabolites produce different types of physical dependence, suggesting that they or their metabolites have different mechanisms and sites of action; 2) plasma cumulation of the benzodiazepines or their active metabolites is an important factor in the genesis of physical dependence; and 3) metabolism of benzodiazepines plays an important role in their dependence-producing capacity, and because of differences in the way species metabolize benzodiazepines, the type of dependence produced in different species may differ.

Administration, Oral↗
PubMed1990

Definition of refractoriness against conventional chemotherapy in acute myeloid leukemia: a proposal based on the results of retreatment by thioguanine, cytosine arabinoside, and daunorubicin (TAD 9) in 150 patients with relapse after standardized first line therapy.

Response to salvage therapy at first and second relapse was analyzed in 150 patients with acute myeloid leukemia (AML) to improve the characterization of relapsed AML and to deduce from this analysis a proposal for the definition of refractoriness against conventional therapy. Salvage treatment consisted of a repetition of the TAD 9 regimen which was already applied as induction protocol at initial diagnosis. All patients were recruited from the multicenter 1982 trial of the German AML Cooperative Group and had thus received a standardized first line treatment. Response at first relapse was significantly related to the duration of the first remission. From 38 patients relapsing within 6 months after successful induction therapy, only 11 (28%) achieved a second complete remission as compared to 58 of 98 (59%) cases with later occurring relapses (p less than 0.01). This difference was due to a significantly higher incidence of persistent leukemia in the former group and not biased by differences in early death rates. No other variable was found predictive for the response to salvage treatment including age, WBC, serum LDH, morphologic subtype, presence or absence of DNA aneuploidy as detected by flow cytometry or maintenance chemotherapy. A low remission rate of 28% was also obtained in the 14 patients at second relapse. These data indicate that patients with a duration of their first remission of more than 6 months cannot be considered as being refractory against standard chemotherapy while patients with early relapses and second recurrences have a response rate of less than 30% due to refractory disease. Hence, the following criteria are proposed for the definition of refractoriness against standard chemotherapy in advanced AML: (a) nonresponse to first-line induction therapy, (b) early relapse within 6 to 12 months of first remission, (c) relapse after 6 to 12 months of first remission and failure on a reinduction attempt with established regimens, (d) second and subsequent relapses. These criteria may provide a useful rationale for the selection of the most appropriate treatment at relapse. They may also serve as eligibility criteria for clinical phase I/II studies and will facilitate interstudy comparisons.

Adult↗
PubMed1989

Nigrostriatal function in humans studied with positron emission tomography.

The dopamine depletion that is characteristic of Parkinson's disease has been hypothesized to result from the combination of environmentally induced subclinical damage to the substantia nigra and the age-related loss of additional nigral neurons. Essential to this hypothesis is the existence of deteriorating function in the nigrostriatal pathway with advancing age. The present study was undertaken with [18F]6-fluoro-L-dopa and positron emission tomography to determine in vivo the effects of age on the nigrostriatal pathway in a series of 10 asymptomatic subjects (age range, 22-80 years; mean, 49.8 years). A graphical approach was used in the analysis of multiple-time tracer-uptake data to establish the presence of a compartment with unidirectional uptake and to calculate the rate constant, K, for uptake of [18F]6-fluoro-L-dopa from blood to striatum during steady-state, an index of the functional integrity of nigrostriatal nerve endings. There was a significant linear relationship between K and age (r = 0.80, p less than 0.005) with a decrease of 53.3% over the age range studied. These results demonstrate the application of a unidirectional transfer model to the analysis of [18F]6-fluoro-L-dopa and positron emission tomography data and provide in vivo confirmation of an age-related impairment of nigrostriatal function.

Adult↗
PubMed1989

Cardiovascular and respiratory effects of an opioid kappa agonist ethylketazocine and sigma agonist N-allylnormetazocine in acutely decerebrated dogs.

Effects of opioid kappa agonist ethylketazocine (EKC), sigma agonist (+-)-N-allylnormetazocine (NANM), and naloxone alone and in combination on mean blood pressure (MBP), heart rate (HR), respiratory rate (RR) and minute volume (MV) were studied in acutely decerebrated dogs. EKC (0.5 mg/kg) decreased HR, MBP, RR and MV. Post-EKC NLX increased RR and MV and reversed the bradycardia and hypotension produced by EKC. NANM (1 mg/kg) produced respiratory depression and tachycardia without changing MBP. Post-NANM NLX antagonized tachycardia, increased MBP, however did not significantly change RR and MV. When decerebrate dogs were spinalized at the C-1 level, EKC decreased MBP and HR. These effects were antagonized by NLX. NANM did not change HR but raised MBP in spinalized decerebrate dogs. Since EKC- and NANM-induced cardiovascular and respiratory depression were not observed in conscious intact or chronic spinal dog, it is suggested that: 1) kappaergic system rostral to mesencephalon may play a role in counteracting these depressant effects of EKC; 2) sigma receptor-mediated tachypnea and tachycardia are dissociable; the tachypneic effect may be mediated through higher center while the medulla oblongata is involved in producing tachycardia. These results also suggest that (+-)-NANM probably has several mechanisms of action at several brain sites in producing its effects on respiration and cardiovascular function.

Animals↗
PubMed1989

Mechanisms involved in the respiratory depressant actions of nicotine in anesthetized rats.

In the urethane-pentobarbital anesthetized rat, the respiratory depressant and lethal effects of intravenously infused (-)-nicotine (120 micrograms/kg/min) or (+)-nicotine (600 micrograms/kg/min) were effectively prevented by pretreatment with the opioid antagonist, naltrexone, whereas the lethal effect of (-)-nicotine (120 micrograms/kg/min) was not altered by bilateral adrenalectomy. Further, pretreatment with either the nicotinic ganglion-blocker, mecamylamine, a secondary amine, or the quarternary nicotinic ganglion-blocker, hexamethonium, completely prevented the lethal effects of (-)-nicotine (120 micrograms/kg/min). These data suggest that central opioidergic and nicotinic processes are involved in nicotine's respiratory depressant and lethal effects.

Anesthesia↗
PubMed1989

PET studies of parkinsonian patients treated with autologous adrenal implants.

Transplantation of autologous adrenal medulla tissue into the striatum has recently been proposed as a treatment for Parkinson's disease. We report the use of positron emission tomography (PET) to evaluate patients who had adrenal implants placed into the right caudate. 6-[18F] fluoro-L-dopa (6-FD) scans were performed to study the integrity and activity of the implant, and the nigrostriatal dopamine system before and six weeks after transplantation surgery. [68Ga] Gallium-ethylenediaminetetraacetate (Ga) scans were also performed to assess the blood brain barrier. The Ga scans performed on two patients showed increased permeability of the blood brain barrier at the surgical site. 6-FD PET scans in five patients did not show a consistent change in striatal uptake following adrenal medullary implantation after six weeks. Further assessment of implant viability with 6-FD PET scans after longer follow up may provide useful information if the blood-brain barrier becomes re-established with the passage of time.

Adrenal Medulla↗